Roller means for applying magnetic material to sound recording tape



Aug. 9, 1955 'w. c. SPEED ET AL 2,714,871 ROLLER MEANS FOR APPLYINGMAGNETIC MATERIAL TO SOUND RECORDING TAPE Filed June 20, 1952 3Sheets-Sheet l INVENTORS W/LL/AM CZ $P E0 JAMEsJOWYER 4%,M, w m wATTORNEYS 3 Sheets-Sheet 3 g- 1955 w. c. SPEED ET AL ROLLER MEANS FORAPPLYING MAGNETIC MATERIAL To SOUND RECORDING TAPE Filed June 20, 1952ATTORNEYS United States Patent ROLLER MEANS FOR APPLYING MAGNETICMATERIAL TO SOUND RECORDING TAPE William C. Speed, Riverside, and JamesJ. Dwyer, Stamford, Conn., assignors to Audio Devices, Inc., New York,N. Y., a corporation of New York Application June 20, 1952, Serial No.294,636 2 Claims. (Cl. 118-449) This invention relates to the productionof magnetic sound recording tape and has for its object improvements inthe method of and apparatus for producing such tape.

It is customary in the production of magnetic sound recording tape topass a long and narrow tape base or band successively from a rollunwinding zone through, usually, an adhesive precoating zone, anadhesive precoat partial drying zone, a magnetic coating zone, and amagnetic coat drying zone to a roll winding zone. To this end there areprovided, in sequential association with each other, a roll unwindingdevice, an adhesive precoating device, an adhesive precoat partialdrying device, a magnetic coating device, a magnetic coat drying machineand a roll winding machine.

The tape base is formed of paper or plastic, such as cellulose acetate.One side is precoated, in whole, in part or parts, with a suitableadhesive liquid, such as a copolymer of polybutadiene withacrylonitrile, the methyl esters of carylic acid, etc. The purpose ofthe adhesive precoating step is to prepare or condition that side of thetape base for receiving and retaining the magnetic coating. A betteradherence of the magnetic coating is assured by the interposition of theadhesive coating between the tape base and the magnetic coating. Theadhesive coating may be regarded as a mid-layer in a laminatedstructure, the tape base being bound to the adhesive coating and themagnetic coating being bound, in turn, to the adhesive coating to forman integral unitary whole. The magnetic material usually is finelydivided, synthetically produced, magnetic oxide of iron in a dispersionof binder and solvent liquids.

A practice such as that briefly referred to is disclosed for example, inour co-pending applications, Serial Nos. 201,974 and 201,977, filedDecember 21, 1950.

The present improvements relate more especially to the adhesiveprecoating operation. Because of its sticky nature, troublesomedifficulties are encountered in the use of adhesive liquids. Even whenoperating with extreme caution, the apparatus employed tends graduallyto become covered, in part at least, with some of the adhesive liquid atmost undesired places. The adhesive liquid may find its way to thereverse side of the tape base, thus impairing if not destroying itsusefulness. The adhesive coating may tend to vary in thickness. It tendsto vary also in its attachment to the tape base, being less securelybonded thereto in some areas than in others.

Eflicient production is aided when the tape base can be passed rapidly,without interruption, through the successive zones mentioned. When suchadhesive precoating dilficulties arise, however, it is necessary oftento stop the passage of the tape base. All power-driven machineryemployed to propel the tape base must beshut down. Time and labor areconsumed to clean up the messes; an aflected section of the tape basemay have to be cut out; its ends must be joined, etc.

Such interruption of the passage of the tape base also affects,unforunately, the magnetic coating operation. The dispersion of magneticmaterial is free flowing and tends 2,714,871 Patented Aug. 9, 1955promptly to spread over surrounding areas of the apparatus. Time andlabor are consumed also in cleaning up that mess. Aifected sections ofthe tape base must be cut out, be spliced, etc., to restore desiredoperating conditions.

Our investigations have led to the discovery that the adhesiveprecoating operation may be conducted in a substantially clean andcontinuous manner. The adhesive liquid is applied and confined solely tothe area desired on the same side of the tape base. So far as theadhesive precoating step is concerned, there is no need to stop theoperation, a selected area only of the apparatus is touched by theadhesive, and the reverse side of the tape base remains free ofadhesive.

These and other features of the invention will be better understood byreferring to the accompanying drawings, taken in conjunction with thefollowing description, in which:

Fig. 1 is a diagrammatic side elevation in section of an apparatusillustrative of a practice of the invention;

Fig. 2 is an end elevation, partly broken away, looking toward themagnetic coat main drying chamber and the winding machine shown in Fig.1;

Fig. 3 is a section on the line 33 of Fig. 1, showing the unwindingdevice of that figure;

Fig. 4 is a plan view of the same;

Fig. 5 is a section on the line 5--5 of Fig. 4;

Fig. 6 is a section on the line 66 of Fig. 4, showing a demountableshaft arrangement for the unwinding device;

Fig. 7 is a section on the line 77 of Fig. 1, showing a tape baseself-aligning device;

Fig. 8 is a plan view of the same;

Fig. 9 is a section on the line 99 of Figs. 1 and 11, showing atransverse end elevation of the pre-coating machine counter to thegeneral direction of travel of the tape base;

Fig. 10 is a plan view of the same;

Fig.- 11 is a longitudinal cross-section on the line 11-11 of Fig. 10;and

Fig. 12 is a transverse end elevation on the line 12-12 of Fig. 11,showing the precoating machine in the general direction of travel of thetape base.

Returning to Fig. 1, which gives one an over-all side view of theapparatus, it will be noted that it may be regarded, in terms ofoperation, as being divided into: (1) roll unwinding zone A; (2)adhesive precoating zone B; (3) adhesive precoat partial drying zone C;(4) magnetic coating zone D; (5) magnetic coat drying Zone E; and (6)roll winding zone F. In terms of apparatus the same zones may beconsidered as (a) roll unwinding device 20; (b) adhesive precoatingmachine 22; (c) adhesive precoat partial drying device 24; (d) magneticcoating device 26; (a) magnetic coat drying machine 28; and (f) rollwinding machine 30. They will be taken up in that order, primaryemphasis being directed to the adhesive precoating zone and machine andthe manner in which it cooperates, particularly, with the adjacent zonesand devices.

Roll unwinding zone Roll unwinding device 20 is shown in Figs. 1, 3, 4,5 and 6. A roll 34 of tape base 36 on a hub 38 is mounted on a core 40,being securable thereto by a key 42. The core in turn is mountedintegrally on the in termediate portion of a removable shaft 44. Thearrangement is such that a roll of tape base to be processed may bemounted on a core-shaft unit in readiness for placement on the rollunwinding device; for example, when a preceding roll is unwound and itscore-shaft unit is removed.

To makesuch action possible, the end portions of the shaft may be fittedin open journals 46 and 48 secured to the tops of side channels 50 and52 fastened to a base 54. The journals (Fig. 6) have an open recess 56limited by a low rear shoulder 58 and a high forward shoulder 60. Thepull or thrust of the roll, as it is unwound, is downwardly toward thehigher shoulders. This restrains the shaft from jumping out of itsrecesses in the journals.

It is important that the tape base from the roll be closely confined ina predetermined path of travel as it goes to adhesive precoating machine22. An adjusting device 64, therefore, is associated with the near endof the unwinding shaft. It includes a threaded lateral rod 66 integrallysecured at its far end to a vertical bar 68 fastened to side channel 50.Rotatably mounted on the rod are a knurled lock-nut 70 and a threadedadjusting member 72. The near end of the latter has a knurled knob 74for easy turning and the far end is provided with an annular recess 76,into which fits an annular shoulder 78 integrally secured to the nearend portion of the unwinding shaft. It will be clear that the adjustingmember may be moved back and forth on the lateral rod and that the shaftin turn will be moved in a corresponding direction. In this manner roll34 may be accurately positioned to unwind tape base 36 in its path oftravel as it advances to be precoated. When the desired adjustment ismade, the lock-nut is turned to maintain the adjusting member in thatposition.

It is important also that the tape base not be unwound from the roll toorapidly. There is a marked tendency for this to occur as the rolldecreases in size and its momentum continues at a high rate. The tapebase should be fed to the precoating zone at the same rate it proceedsthrough the magnetic coating and magnetic coat drying zones.

A brake device 82 (Figs. 3, 4, and is provided for regulating andcontrolling the rate of unwinding of the tape base from its roll. Thedevice includes a brake block 84 on the top of a lateral arm 86 pivotedat one end 88 to side channel 52. The brake block is directly below andin frictional engagement with a circular brake disc 90 mountedintegrally on the far end portion of the unwinding shaft. The other endof the arm is fitted with a vertical threaded rod 92 extending through alateral bar-support 94 attached to the top of the same side channel.Mounted on the upper end of the rod is a lock-nut 96 and a threadedadjusting member 98. The upper end of the latter contains a knurled handknob for easy turning. It will be clear that the arm may be pivoted upor down by turning the adjusting member; that the amount of brakingaction of the brake block on the brake disc may thus be regulated fromtime to time, as required, and that the lock-nut may be turned to lockthe adjusting member against the bar support.

Adhesive precoating zone Adhesive precoating machine 22 is shown inFigs. 1, 7, 8, 9, 10, 11 and 12. As shown in Fig. 1, the tape basepasses forwardly and downwardly from the roll to and around a transverseguide rod 102; horizontally forward to and around a second transverseguide rod 104; upwardly to and around a self-aligning guide roller 106;horizontally to and between a pair of superposed rollers 110 and 112;and around the latter roller to adhesive precoat partial drying device24.

Guide rods 102 and 104 are fixed, preferably, so that they may help toexert braking action on the tape base at its leaves the roll. They aresecured at their ends in side supports, as indicated in Fig. 1.

Self-aligning guide roller 106 (Figs. 7 and 8), on the other hand, issuspended between two pivot pins 116 and 118. The main body portion ofeach pin is threaded to fit in threaded holes in the depending legs of apivoting channel bracket 120. Lock-nuts 122 and 124 are used to securethe pins and hence their pivot points in an optimum position for therotation of the guide roller. The bracket is suspended on a vertical rod126 extending through a crossbar support 128 and a roller-bearing 130 tofacilitate pivoting of the guide roller. As the tape base passes overthe roller, the roller is free to oscillate back and forth to keep thetape base aligned or centered in its path of travel to the rollers.

The rollers, preferably, are formed of material, such as rubber, topermit gripping of the tape base as it passes between them. Upper roller112 is mounted on a power'driven shaft 134 supported in journals 136 and138 attached to the tops of side channels 50 and 52. A fly wheel 140 ismounted on the far end of the shaft. The same end portion of the shaftis fitted with a sprocket wheel 142, fitted with a sprocket chain 144extending to a sprocket-wheel 146 on the near end of the drive shaft ofa motor 148 secured to a platform 1S0 attached to side channel 52.

Lower roller 110 is mounted on a floating shaft 152 suspended at itsends in journals 154 and 156 attached to the tops of lateral arms 158and 160 pivoted at their right ends, as one views Figs. 1 and 11, tobrackets 162 and 164. Springs 166 and 168 are attached at their lowerends to the left ends of the lateral arms; and at their upper ends tothreaded rods 170 and 172, extending through Z-lugs 174 and 176 attachedto the tops of channels 50 and 52. Wing nuts 178 and 180 on the upperends of the rods permit raising or lowering the lateral arms, and hencethe amount of pressure exerted by the rollers on each other and on thetape base passing between them.

A removable pan 184 is located directly below the lower roller, thelower portion of the roller extending Well into the pan, and into a bodyof adhesive liquid 186, maintained at a level 188 by means of anautomatic feed line 190. The pan is secured (Figs. 11 and 12) to anangle support 192, the ends of which extend over the right end portionsof lateral arms 158 and 160. The bottom leg of the angle support isprovided (Fig. 10) with open slots 194 and 196, respectively, over thelateral arms. Threaded rods 198 and 200 extend through threaded holes inthe arms, the upper ends of the rods terminating in knurled hand knobs202 and 204. It will be clear that the pan may be locked in positionunder the lower roller by turning the knobs. This arrangement alsopermits the removal of the pan, say at the end of a work day or period,for cleaning or any other desired purpose.

As shown in Fig. 11, the upper roller turns counterclockwise, and thelower roller is caused to rotate in a clockwise direction; again, as oneviews Figs. 1 and 11. The lower roller contains a great many uniformlyspaced small surface pockets 206 (Fig. 12) of optimum size. Since theroller dips into the pan, the pockets are filled with adhesive which iscarried toward the tape base. i

To make certain that a metered amount of adhesive is thus conveyed tothe tape base, a doctor blade 208 is used (Figs. 1, 9, 10 and 11). 'Itis secured to a crossplate 210 mounted pivotally on a cross-rod 212. Theends of the cross-rod fit in brackets 214 and 216 and the cross-rod isheld in fixed position by set screws 218 and 220. The cross-plate anddoctor blade are adjustable as a unit with respect to lower roller 112.To this end springs 221 and 223 are fastened at their lower ends to theforward portion of the cross-plate and at their upper ends to anchors222 and 224. A pair of spaced arms 226 and 228 are mounted on thecross-rod 212, being integrally secured thereto by set-screws 230 and232. The forward end of each arm has a threaded hole through whichextends a threaded adjusting rod 234, having a lock-nut 236. With thisarrangement, the rods can be turned to regulate and locked to fix theamount of pressure of the doctor blade on the lower roller, and

hence to level otf and control the amount of adhesive liquid thatreaches the under-side of the tape base pass ing between the rollers. Asshown to advantage in Fig. 11, the adhesive coated tape base movesaround the right half portion of the upper roller, the uncoated side,however, only being in contact with that roller.

Before tracing the further progress of the tape base, several items ofimportance should be noted. The lower roller is somewhat narrower thanthe upper roller. The lower roller is narrower, in turn, than the tapebase so that its marginal edge portions 238 and 240 (Figs. 9 and 10) donot contact that roller and hence are not coated with adhesive liquid,the intermediate portions 242 only being coated. The tape base, on theother hand, is narrower than the upper roller so that the tape base isfully supported transversely by that roller. That support helps to keepthe freshly coated tape base from warping as well as to keep it in itsnormal path of travel. Also, as already indicated, the pressure of therollers may be regulated to work the adhesive liquid thoroughly thereon,thus to assure a uniformly good bond between the two, as Well as topropel the tape base in its path of travel. The rollers,- particularlywhen under substantial pressure, appear to grind or rub the adhesiveinto the pores of the tape base, thus assuring a firm unitary structure.

Adhesive precoat partial .drying. zone Adhesive precoat partial dryingdevice 24 is shown in Fig. 1. It includes a guide rod 250 to direct thetape base, precoated side uppermost, horizontally through an elongateddrying tunnel 252 having a glass top 254. A bank 256 of electric lightbulbs, preferably infra-red bulbs, extends across the glass top so thatradiant heat may be applied to the adhesive precoat. As indicated, theadhesive is only partly dried. The magnetic material appears to form abetter bond with a partially dried adhesive precoat than with a whollyundried one, at least with the adhesive liquids now used. It would beinadvisable, of course, completely to dry the adhesive precoat at thisstage. To do so would defeat the very purpose of the adhesive coatingstep. The amount of drying can be controlled in various ways, such as bythe speed of travel of the tape base through the tunnel, the length ofthe tunnel, the number and intensity of the bulbs in the bank, etc.

Magnetic coating zone Magnetic coating device 26 is shown in Fig. 1. Itincludes guides 260 and 262 to direct the partially dried tape basebetween a bottom support 264 mounted on springs 266 and a fixed feedhopper 268, which receives a dispersion of magnetic material 270 througha feedline 272. As the tape base passes under the hopper, its partiallydried adhesive precoat receives a coating of the magnetic material. Thetwo coatings are bonded easily and quickly to form a firm integralunitary whole.

Magnetic coat drying zone Magnetic coat drying machine 28 is shown inFigs. 1 and 2. Going to the former, it will be noted that the magneticcoated tape base passes around a gripping roller 276 downwardly throughan inclined extending duct 278, where it meets air heated by a heater280 and blown by a fan, not shown; that the tape base thus partiallyair-dried passes through an extension 282 of the duct, with a glass top284 over which is a bank 286 of infra-red bulbs, for further drying byair and radiant heat; and that the tape base then moves into a finaldrying chamber 288 where it is heated by additional banks 290 and 292 ofsimilar bulbs, through glass side 294 and glass top 296, as the tapebase pursues a tortuous, more or less zig-zag, but extensive course oftravel around a plurality of spaced guides to an exit opening 298.

Power to propel the tape base along its long course is obtained througha motor 300; a gear-reducer 302, the speed of which is controlled by wayof a hand-wheel 304 (Fig. 2);- a sprocket chain 306 (Fig. 2); a driveshaft 308 (Figs. 2 and l); and drive belts 310 connecting the driveshaft and guide rollers.

During its passage through the chamber, the coatings on the tape baseare well dried by the heated air and radiant heat. Binder and solventliquids are gradually volatilized and escape, with the spent air,through a vent 312, preferably to the outside atmosphere.

Roll winding zone Roll Winding machine 30 is shown in Figs. 1 and 2. Itincludes, briefly, a winding shaft 316 supported on its far side injournals 318 and 320 secured to a platform 322. The near end of theshaft is fitted with a core 324. As shown in Fig. l, a hub 326 is fittedon the core, being secured thereto by a key 328 (Fig. 2). The dried tapebase issuing from the main drying chamber, through exit opening 298, isshown being wound into a roll 330 on the hub.

The far end of the Winding shaft terminates in a sprocket wheel fittedwith a sprocket chain 332. The sprocket chain also fits over a sprocketwheel on the near end of the driven shaft of an automatic speedcontroller 334. The far end of the driven shaft terminates in a sprocketwheel fitted with a sprocket chain 336 which is mounted also on asprocket wheel on the far end of the drive shaft of a motor 338.

A linear length or footage counter 340 is located ad jacent the roll, Itis in the form of a housing 342 secured to the free end of a lateral arm344 pivotally connected to a vertical support 346 resting on theplatform. The shaft 348 of the counter terminates in a friction disc 350adapted to engage and ride on the upper surface of the tape base as itis wound onto the roll. Due to the manner in which the counter ispivotally mounted, the friction disc rises automatically as the diameterof the roll increases.

Speed controller 334 regulates the speed of rotation of winding shaft316 so that it automatically adjusts itself to whatever speed isrequired to roll the dried tape base as fast as it issues from thedrying chamber. In other words, the rotational speed of the windingshaft is gradually reduced as the roll increases in diameter.

When the desired amount of dried tape base is wound onto the roll, motor338 is stopped. The dried tape base is cut transversely intermediate theexit opening and the roll; the roll and its hub are removed as a unitfrom core 324, and an empty hub is placed on the core to permit thestarting of another roll of dried tape base.

It will be clear to those skilled in this art that the specificembodiment described is by way of illustration and that the practice ofthe invention readily lends itself to the use of other embodiments.

We claim:

1. In apparatus for producing magnetic sound recording tape by advancinga long narrow tape base successively from a roll unwinding devicethrough an adhesive precoating device, a precoat partial drying device,a magnetic coating device and a magnetic-coat drying machine to a rollwinding machine, the improvement comprising an adhesive precoatingmachine which includes a vessel for containing and supplying adhesiveliquid to one side of the tape base, a pair of opposed superposedpressure rollers mounted over the vessel for the application of theadhesive liquid to and the passage of the adhesive coated tape basetherebetween to level off the adhesive liquid, to provide a good bondbetween the tape base and the adhesive coating; the lower roller havinga cylindrical adhesive applying surface shorter than the upper rollerand disposed intermediate the ends of the upper roller and extendingpartly into the vessel and below the level of the adhesive liquidnormally confined therein, so that the cylindrical adhesive applyingsurface of the lower roller may be wetted with and thus transferadhesive liquid to said side of the tape base; the lower cylindricaladhesive applying surface being narrower than the tape base and disposedonly across the intermediate transverse portion of the taperbase so thatits marginal edge portions will not be coated with the adhesive liquid;the outer cylindrical adhesive applying surface of the lower rollerbeing provided with a plurality of spaced small surface pockets to befilled with adhesive liquid; and a doctor blade extending transverselyacross the lower roller between the adhesive liquid level of the vesseland the upper roller to level ofl? such liquid in the pockets and forremoving excess adhesive liquid from the cylindrical adhesive applyingsurface of the lower roller before it contacts the tape base.

2. In apparatus for producing magnetic sound recording tape by advancinga long narrow tape base successively from a roll unwinding devicethrough an adhesive precoating device, a precoat partial drying device,a magnetic coating device and a magnetic-coat drying machine to a rollwinding machine, the improvement comprising an adhesive precoatingmachine which includes a vessel for containing and supplying adhesiveliquid to one side of the tape base, a pair of opposed superposedpressure rollers mounted over the vessel for the application of theadhesive liquid to and the passage of the adhesive coated tape basetherebetween to level off the adhesive liquid, to provide a good bondbetween the tape base and the adhesive coating; the lower roller havinga cylindrical adhesive applying surface shorter than the upper rollerand disposed intermediate the ends of the upper roller and extendingpartly into the vessel and below the level of the adhesive liquidnormally confined therein, so that the cylindrical adhesive applyingsurface of the lower roller may be wetted with and thus transferadhesive liquid to said side of the tape base; the lower cylindricaladhesive applying surface being narrower than the tape base and disposedonly across the intermediate transverse portion of the tape base so thatits marginal edge portions will not be coated with the adhesive liquid;the lower roller being mounted on a shaft resting at its ends in a pairof journals; each journal being supported by a pivoting arm intermediateits ends; one end of each arm being pivoted to a fixed bracket and theother end being resiliently supported by a spring; and adjusting meansfor increasing and decreasing the tension of the springs and thusincreasing and decreasing the pressure of the rollers on the tape basepassing between them.

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